Monsanto (NYSE: MON) has been a major investor in genetically modified (GM) crops, and that investment has generated a lot of green for the company. In the U.S., the largest market for the agricultural technology outfit, it has grown its share in corn seeds in particular, so now it's the market leader with a 51% share. It's an impressive business -- Monsanto's corn seed and traits segment brought in $1.08 billion in sales in the first six months of this fiscal year.